I would have asked for pilots to give their license number and name in an effort to establish the veracity of the respondents. I know from experience that there were a few people who signed the petition using false names - the usual suspects I suppose. Most surveys attempt to avoid this problem by preventing users with the same ISP completing the survey a second time, or asking the person for their email address so that an ISP and corresponding email is prevented from having a second go. None of these techniques are perfect, but given that a third party (iSalient) is presumably being paid to do the job I would expect them to consider this issue (as indeed they might well have done).
I have some other comments but as the survey is under way this is not the time.
Bose - how are you intending to ensure as many pilots as possible are aware of the survey? (Excluding those here, AOPA members and readers of one of the GA mags.) It is surprising how many pilots do not follow these sources of news. I might have included a question along the lines - How did you hear about this surey?